The Channel Tunnel (; also referred to as the Chunnel) is a rail tunnel linking Folkestone, Kent, in the United Kingdom, with Coquelles, Pas-de-Calais, near Calais in northern France, beneath the English Channel at the Strait of Dover. At its lowest point, it is deep. At , the tunnel has the longest undersea portion of any tunnel in the world, although the Seikan Tunnel in Japan is both longer overall at and deeper at below sea level. The speed limit in the tunnel is .